Electric motor



M. ISAACSO N ELECTRIC MOTOR April 23, 1963 Original Filed Jan. 17, 1957 $387,030 ELECTRIC MOTQR Max Isaacson, Dayton, Ohio, assignor to Iohe Industries, Inca, Dayton, Ohio, a corporation of Ohio Griginai appiication Jan. 17, 1957, Ser. No. 634,723, now

Patent No. 2,936,665, dated May 30, I961. Divided and this application Feb. 6, 1961, Ser. No. 37,259

It) Ciaims. (Ci. 310-454) This invention pertains to an electric motor utilizing either permanent or electromagnets and the method of producing the same.

In the Robert A. Stein copending application Serial No. 471,560, there is disclosed a method of manufacturing a stator for an electric motor of the permanent magnet type. In the Stein application the pole pieces are all parallel to each other and parallel to the axis of rotation of the armature.

It is quite desirable to have an askew relationship between the armature slots and the pole faces of an electric motor. In a small electric motor, it has been found much easier to wind the rotor or armature when the slots are parallel to the axis of rotation of the armature. Furthermore, in order to obtain the desired askew relationship, it may be necessary in some cases to arrange the poles in askew relationship and the armature slots in askew relationship, but in the opposite direction, so as to obtain the proper angular displacement of the poles with respect to the armature slots.

By arranging the poles and the armature slots in an askew relation to each other, the magnetic drag is reduce-d, and a steadier pull is applied to the armature or rotor, in that pulsations are reduced. Furthermore, it has been found that a smaller current is required to start the motor when there is an askew relationship between the armature slots and the poles. In other words, for a given current, the starting torque is greater when this askew relationship exists. It is also advantageous as far as the commutation is concerned to have this askew relationship.

In producing small electric motors of the permanent magnet type, it is quite desirable that the ends of the permanent magnet contact the pole engaging facets of stationary pole members in planes parallel to the axis of rotation of the rotor. That being the case, it has not been found practical to askew the entire pole pieces and the contacting surfaces between the poles and the permanent magnets, in that any misfit or misalignment of the ends of the permanent magnets with respect to the contacting surfaces of the poles greatly reduces the efficiency of the motor, for the reason that the reluctance is greatly increased.

An object of this invention is to provide an electric motor wherein the contacting surfaces between the permanent magnets and the magnet contacting surfaces of the poles extend in planes parallel to the axis of rotation of the rotor and wherein the pole piece overlying the armature or rotor is angularly displaced with respect to the axis of rotation of the armature, so as to obtain an askew pole piece but, at the same time, maintain contact between the poles and the permanent magnets in planes parallel to the axis of rotation of the rotor. This has been accomplished by the use of the angularly displaced channels or rabbets tapering as to depth and located between the portion of the pole that is in contact with the permanent magnets and the pole face adjacent the armature or rotor.

As is disclosed in the aforementioned Stein application, non-magnetic material is cast on the ends of the two poles which poles are held in fixed spaced relation. In addition to the Stein disclosure, the tapering channels or rabbets States Fatent 9 3,937,080 Patented Apr. 23, 1963 are filled with a non-magnetic material, so that when machining the pole faces, the cutting tool passes from one type of material to another type along the margins of the askew portions forming the pole faces of the pole pieces, thereby eliminating burrs being formed along the margins of the pole pieces.

Another object of this invention is to provide pole pieces that may be made from powdered metal, wherein each pole piece may be made in two parts, each part being made in the same mold cavity, so that when juxtaposed upon each other, the proper askew relationship is obtained by the use of a comparatively simple mold used in forming the powdered metal.

Another object of this invention is to provide a four pole stator, wherein the pole pieces are askew with respect to each other and wherein one pair of pole pieces are made from two pieces juxtaposed upon each other and the other pair of pole pieces are made from two pieces juxtaposed upon each other, this being followed by casting non-magnetic material on the ends of the pole pieces arranged in quadrature, so as to firmly hold the pole pieces in fixed position, the piece used in forming the pole pieces including portions forming facets adapted to be in contact with the ends of the permanent magnets, which facets lie in planes parallel to the axis of rotation of the armature. The faces of the pole pieces that are located adjacent the armature are provided with diagonaily disposed rabbets, to thereby present an askew pole face adjacent the rotor or armature.

' Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacturing and the mode of operation, as will become more apparent from the following description.

Referring to the drawings,

FIGURE 1 is an end view of a magnetic bar having the ends cast in non-magnetic material.

FIGURE 2 is a side elevational view of the bar and the cast non-magnetic material shown in FIGURE 1.

FIGURE 3 is a cross sectional view, taken substantially on either section line 3-3 of FIGURE 2.

FIGURE 4 is a cross sectional view, taken substantially on the line 44 of FIGURE 2.

FIGURE 5 discloses pole pieces that are made from powdered metal, each pair of pole pieces being made from two identical pieces juxtaposed upon each other.

FIGURE 6 is a side elevational view of the pole pieces disclosed in FIGURE 5 after having been assembled and having non-magnetic material cast on the ends throughout the core.

FIGURE 7 is a cross sectional view, taken substantially on the line 77 of FIGURE 6.

FIGURE 8 discloses a pair of pieces that, when juxtaposed upon each other, form a single pair of poles.

FIGURE 9 is a transverse cross sectional view of a finished stator having two poles and the permanent magnets.

FIGURE 10 is a transverse cross sectional view of a finished stator having four poles made from powdered metal.

Referring to the drawings, the reference character It) indicates a piece of magnetic material that has been severed from a bar of magnetic material. This piece of magnetic material has been provided with parallel facets i2, i4, 16 and 13. The facets 12, 14, 16 and 18 are preferably machined surfaces, so that all the surfaces are parallel to each other. For convenience, arcuate slots or notches 20 have been formed in the outer margins. The piece 10 is provided with an enlarged center portion 21, best seen in FIGURE 4 and shown by dotted iines in FIGURE 1.

Diagonal slots or grooves 22, 24, 26 and 28 have been cut in the Zone located between the parallel facets 12, 14,

a T6 and 18 and the enlarged portion 21. The grooves 22 and 24 have parallel bottoms and the grooves 26 and 2? have parallel bottoms. As best seen in FIGURE 3, an intermediate portion St is diagonally disposed or askew with respect to the longitudinal axis of the original bar. The slots or grooves form rabbets that taper from one end to the other. Furthermore, adjacent grooves taper in opposite directions. The grooves have been cut or formed in a manner such that the pole faces are all askew in the same angular direction with respect to the slots in the armature.

After the grooves have been formed, the piece it is placed in a mold having cylindrical cavities into which the ends of the piece 19 project. By pouring non-magnetic material into the two ends of the mold, castings 4t) and 42 are formed. The casting 42 is provided with a cylindrical extension 44. This non-magnetic material also fills the grooves 22, 24, 26 and 28. The castings 4t? and 42 are machined by any suitable mechanism, as for example, a turret lathe. The centers of the castings and the piece are drilled or machined, so as to provide a hole, this hole dividing the piece 14) into two pole pieces, the pole faces 23 being arranged askew with respect to the longitudinal axis.

The operations of drilling the hole and trimming the piece have been fully described in the copending Stein application Serial No. 471,560. At this time the detailed operations will not be repeated. Sutfice to state, that as the hole is drilled or machined through the center of the piece 10, no burr will be formed on the margins of the pole face areas, due to the fact that the cutting instrumentality passes from non-magnetic material into the magnetic material and then again into the non-magnetic material. After the center has been machined out, so as to provide two pole pieces having faces 23 that are arranged aske w with respect to the longitudinal axis of the armature mounted in the hole or the bore, the non magnetic material seated in the grooves may be removed, if desired. By placing permanent magnets 4-5, shown in FIGURE 9, each of which is arcuate, against the facets 12, 14, 16 and 18' of the two pole pieces, a magnetic circuit is provided. The magnetic flux linking the armature passes into the armature from the askew pole faces 23.

Instead of using solid bar stock, the magnetic pole pieces may be made from powdered magnetic material that has been molded or preformed and sintered, so as to bind the magnetic material into a unitary structure. In order to facilitate production by the use of a simplified mold, the pole pieces are molded in two parts or halves, as clearly shown in FIGURE 8, that is, the halves 69 and 62. These two halves are identical, molded from the same mold. Each of these halves is provided with portions that form the pole pieces 64 and 66. The front side of each half has a contour of the finished stator frame. The rear surface lies in a plane with the exception of a recess 63 and a projection 65. By superimposing the two halves back to back, a pair of pole pieces is formed, held in spaced relation by the bridging portions 3i) spanning the distance between the poles. The projections 65 are then seated in the recesses 63 to properly align the pole pieces that are welded together, as indicated at 67.

Instead of grooves, rabbets 68 and 7t are used. The two pole pieces 64 and 66 are held together by means of a bridging portion 30 located near one end of the pole pieces. The two halves 6b and 62 are superimposed upon each other, as clearly shown in FIGURE 5. The angular relation of the rabbets 63 and 7t? forms an intermediate portion 72, a portion of which is formed from one of the pieces and the remaining portion from the other piece. The portions are askew with respect to the longitudinal axis, so as to form askew faces adjacent the armature.

In the event a two pole motor is to be produced, the two parts or halves 6t and 62 have the ends and the rabbet provided with castings similar to those described in connection with the preferred embodiment. The bridging portions 89 are embedded in the non-magnetic casting on one of the ends. The bridging portions are removed when the hole for the armature is formed. The pole pieces 60 and 62, together with the bridging portion 8%), cooperate to form a substantially U-shaped member.

A similar arrangement of poles may also be used in connection with a four pole motor, in which event two additional pieces 169a and 1621:: are assembled so as to form a cross. However, in this modification, the bridging portion at the end has been omitted and instead, bridging portions 1% and 1&2 have been used. The face Tilda coincides with a plane bisecting the length of the finished pole pieces. Each of the halves T69 and 162, 166a and 162a is provided with recesses and projections 65 similar to those shown in FIGURE 5 the two pairs of poles have been shown in an exploded view.

The two pairs of pole pieces, as seen in FIGURE 2, have been welded together at 67, or at any other suitable place. The two pairs of pole pieces are moved together along the dotted lines, as shown in FIGURE 5, until the faces of the bridging members and 162 of one pair or set of pole pieces are in contact with the bridging members 1th) and MP2 of the other pair. The two pairs of pole pieces are then, so to speak, nested together, the total width of members and 162 being equal to the spacing between the pole pieces of one pair, so that when the two pairs are nested together, they are in proper fixed spaced relation with each other. The bridging portions 1% and 1432 of one pair of pole pieces may be clamped against the bridging portions 1% and T32 of the other pair of pole pieces, or these bridging portions may be welded together, so as to hold the pole pieces in proper spaced relation.

The four pole pieces are arranged in quadrature, as clearly seen in FIGURES 7 and 10. The non-magnetic material and 92 is then cast on the two ends, the nonmagnetic material filling the rabbets, as clearly seen in the cross-sectional view shown in FIGURE 7. This cros"- sectional view discloses the non-magnetic core 94. By drilling or machining a hole, so as to remove the core and the extreme inner margins of the four pole pieces, a four pole motor is produced, having all of the poles arranged in askew relation, properly spaced. This drilling or machining operation severs the bridging portions and 162, so as to magnetically separate the two parts forming each pole from the other poles. The pole pieces, after the core has been removed, have their ends fixedly embedded in the end castings 99 and 92. The rotor may be mounted in a manner similar to that disclosed in the copending Stein application Serial No. 471,560.

In FIGURE 9 of the drawings, permanent magnets have been used. Instead of permanent magnets, these magnets could be electromagnets, that is, the arcuate members could be provided with windings, or notches could be provided in the pole pieces 12 for the reception of field windings. The invention disclosed herein is not dependent upon the particular type or source of flux. In other words, it could be permanent magnets or it could be electromagnets.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

This application is a divisional application of my copending application Ser. No. 634,723, filed January 17, 1957, now Patent No. 2,986,665.

What I claim is:

1. A pair of half elements for use as pole pieces in an electric motor, each element being identical in shape with its front side having the desired contour of one half of each pole piece and its rear side being substantially planar, the two portions being mated to form a pair of pole pieces with their back sides juxtaposed one another.

2. The half elements of claim 1, wherein each half element consists of a pair of polar portions joined by a bridging portion holding the polar portions in spaced relation.

3. A pair of halves as set forth in claim 1, wherein each half is provided with oppositely disposed polar portions, each of which has an angularly disposed rabbet, the rabbet of one polar portion having its deepest portion in one end, and the rabbet of the other polar portion having its deepest portion in the opposite end.

4. A method of manufacturing the stator for an electric motor of the permanent magnet type, said method including the steps of forming blanks from powdered magnetic metal, sintering said blanks, each of said blanks including a pair of polar portions, one end of each of the polar portions being joined by a bridging portion holding the polar portions in spaced relation, each of the polar portions having a rabbet tapering from one end to the other, the direction of taper of one rabbet being opposite to the direction of the taper of the other rabbet, the rear surface of the blanks lying in a plane, superimposing two blanks upon each other back to back, casting nonterro-magnetic material so as to embed the ends of the polar portions and to fill the rabbets and forming a hole through one of the castings, said hole continuing between the polar portions and through the bridging portion to provide a cavity for an armature.

5. A method according to claim 4, wherein the cast metal in the rabbets is removed therefrom.

6. A method of manufacturing the stator for an electric motor of the permanent magnet type, said method including the steps of forming blanks from powdered magnetic metal, sintering said blanks, each of said blanks including a pair of polar portions, one end of each of the polar portions being joined by a bridging portion holding the polar portions in spaced relation, the rear surface of the blanks lying in a plane, superimposing two blanks upon each other back to back, casting non-ferromagnetic material so as to embed the ends of the polar portions and forming a hole through one of the castings, said hole continuing between the polar portions, and severing the bridging portion to provide a cavity for an armature.

7. The method of producing a four pole stator for an electric motor, said method including the steps of forming two pairs of diametrically disposed pole pieces, each pair being held in fixed spaced relation by a bridging portion extending between the ends of the poles of said pair, the pole pieces and the bridging portion forming a U-shaped structure, arranging one pair of pole pieces with the free ends directed towards the bight of the other pair so that the pole pieces are arranged in quadrature and the bridging portion of the other pair being located at one opposite end thereof, holding the pole pieces in position, casting non-magnetic material on the ends of the pole pieces so as to embed the ends thereof, and forming holes through the castings, at least one of the holes having the same diameter as the diameter between opposite poles through which the armature of the motor extends, the forming of the holes severing the bridging portion so as to magnetically separate the pole pieces.

8. The method according to claim 7, including the steps of forming taperin rabbets along the inner margins of the pole pieces, the taper of adjacent rabbets being directed in different directions, and casting non-magnetic material in said rabbets.

9. The method of producing a four pole motor according to claim 7 including the steps of forming the pole pieces from ferrous magnetic powdered material, and sintering the powdered material to bind the powdered material into a unitary structure.

10. The method of producing a four pole motor according to claim 7, including the steps of forming each pair of pole pieces from two identical halves, and superim posing the two halves together to form the pole pieces.

References Cited in the file of this patent UNITED STATES PATENTS 1,314,132 Dorsey Aug. 26, 1919 2,433,390 Packer Dec. 30, 1947 2,655,611 Sherman Oct. 13, 1953 

1. A PAIR OF HALF ELEMENTS FOR USE AS POLE PIECES IN AN ELECTRIC MOTOR, EACH ELEMENT BEING IDENTICAL IN SHAPE WITH ITS FRONT SIDE HAVING THE DESIRED CONTOUR OF ONE HALF OF EACH POLE PIECE AND ITS REAR SIDE BEING SUBSTANTIALLY PLANAR, THE TWO PORTIONS BEING MATED TO FORM A PAIR OF POLE PIECES WITH THEIR BACK SIDES JUXTAPOSED ONE ANOTHER. 